The present invention relates to a liquid crystal device for displaying information by controlling alignment of liquid crystal encapsulated between a pair of substrates. The present invention also relates to an electronic apparatus configured by using the liquid crystal device.
Currently, in electronic apparatuses such as mobile phones and mobile information terminals, liquid crystal devices are widely used for displaying information, such as characters, numerals, and pictures.
In the liquid crystal devices, for example, pixels are formed by crossing scanning electrodes formed on one substrate and selection (data) electrodes formed on the other substrate at a plurality of points in the form of a dot matrix. Liquid crystal is encapsulated between the substrates and light passing through liquid crystal at each pixel is modulated by selectively changing a voltage applied to the pixel, and thus, images, such as characters, are displayed.
In the liquid crystal device, in order to secure a connecting area for connecting liquid crystal driver ICs and external circuits additionally connected to the liquid crystal device, a protruding portion protruding outside from the area in[at] which the liquid crystal is encapsulated is provided in at least one of the substrates. In addition, in general, the scanning electrodes or the selection electrodes extend from the area at which the liquid crystal is encapsulated to the protruding portion so as to form extending portions reaching the connecting area. Thus, the scanning electrodes or the selection electrodes are connected to the external circuit via the extending portions formed at the protruding portion.
In a so-called reflective or transflective liquid crystal device, a metal having a high reflectance is used as a material for the scanning electrodes or the selection electrodes, and scanning electrodes or selection electrodes may also be used as an inside reflector in some cases. In particular, when aluminum is used as an electrode material, there is a problem in that the extending portions of individual electrodes at the protruding portion are damaged or are readily electrolytically corroded. Electrolytic corrosion is a phenomenon in which electrodes are depleted by corrosion caused by an interaction between various elements, such as bases present at the protruding portion, potential difference between electrodes, and moisture in the air. When electrolytic corrosion occurs, problems of non-illuminated lines due to breakage of the electrodes and the like occur.
In addition, when the extending portions of individual electrodes are exposed, there is a risk of short-circuits between electrodes caused by electrically conductive foreign materials which may contact the protruding portions of electrodes.
In order to prevent damage, corrosion of electrodes, and short-circuits between electrodes, conventionally a structure covering the protruding portion of the electrodes is known, in which a coating material composed of, for example, a silicone, is coated onto the surface of the protruding portion and is adhered thereto. By the structure thus described, contacts of foreign material and the like with the extending portions of the electrodes can be avoided and the influence of moisture is suppressed to some extent. However, even though damage of the electrodes caused by foreign material and short-circuits between the electrodes can be prevented by the method of adhering the coating material mentioned above, it has been difficult to completely avoid electrolytic corrosion due to insufficient sealing properties against water and the like caused by the properties of the coating material or an insufficient adhering state thereof.
An object of the present invention is to provide a liquid crystal device in which electrolytic corrosion of electrodes provided at a protruding portion of a substrate can be prevented, and to provide an electronic apparatus provided with the liquid crystal device.
A liquid crystal device of the present invention comprises a pair of substrates, each having an opposing face opposing each other with liquid crystal interposed therebetween, and each opposing face is provided with electrodes; a protruding portion provided at one of said pair of substrates protruding toward the outside from the other substrate; aluminum electrodes formed on the protruding portion and being in electrical contact with the electrodes; and an overcoat layer composed of an inorganic substance covering the aluminum electrodes.
According to the liquid crystal device, since the aluminum electrodes formed on the protruding portion are covered with the overcoat layer composed of an inorganic substance having superior sealing properties, penetration of water to the aluminum electrodes can be effectively avoided, and hence, electrolytic corrosion of the aluminum electrodes can be reliably prevented.
The liquid crystal device may further comprise an insulating layer covering the electrodes formed on one of said pair of substrates, and the overcoat layer may be formed as the same layer as the insulating layer.
In this case, since the overcoat layer and the insulating layer can be simultaneously formed, the overcoat layer can be formed without complicating the manufacturing process.
The overcoat layer may be formed by a sol-gel reaction.
In this case, compared to the formation of a silicon oxide film as an overcoat layer by a sputtering method, the configuration of manufacturing apparatuses is simple and inexpensive, and the yield can be improved because of a simpler manufacturing process. In cases where a coating material is cured to cause a sol-gel reaction thereby forming an overcoat layer, it is not required to add a step for patterning the overcoat layer because the coating material can be coated in a predetermined shape using a printing method.
The electrodes formed on one of said pair of substrates may be composed of aluminum and may be formed as the same layer as the aluminum electrodes.
In this case, a preferable structure as a reflective or a transflective liquid crystal panel can be obtained.
The aluminum electrodes may be provided with terminal portions to be connected with external circuit connecting portions, and the overcoat layer may be formed so as not to cover the terminal portions.
In this case, since the surfaces of the terminal portions are exposed, the external circuit connecting portions can be reliably connected to the terminal portions.
The terminal portions and the external circuit connecting portions may be connected to each other via an anisotropic conductive film provided at the terminal portions. In this case, the terminal portions and the external circuit connecting portions may be connected to each other in a state in which a part of the overcoat layer is overlaid with a part of the anisotropic conductive film.
In this case, since the entirety of the aluminum electrodes is covered with at least one of the overcoat layer and the anisotropic conductive film, penetration of water and the like to the entirety of the aluminum electrodes can be effectively prevented.
The terminal portions and the external circuit connecting portions may be connected to each other in a state in which there is an area at which the overcoat layer and the connecting portions overlap each other.
In this case, the anisotropic conductive film provided at the area of the connecting portions is overlaid on a part of the overcoat layer in a connecting step, and as a result, the entirety of the aluminum electrodes is covered with at least one of the overcoat layer and the anisotropic conductive film. Consequently, penetration of water and the like to the entirety of the aluminum electrodes can be effectively prevented.
The terminal portions and the external circuit connecting portions may be connected to each other in a state in which an edge face of the overcoat layer and an edge face of the connecting portions oppose each other.
In this case, the anisotropic conductive film provided at the area of the connecting portions is overlaid on a part of the overcoat layer by a flow that occurs when the anisotropic conductive film melts in a connecting step, and as a result, the entirety of the aluminum electrodes is covered with at least one of the overcoat layer and the anisotropic conductive film. Consequently, penetration of water and the like to the entirety of the aluminum electrodes can be effectively prevented.
After a part of the anisotropic conductive film is overlaid on a part of the overcoat layer, the anisotropic conductive film may be melted so that the terminal portions and the external circuit connecting portions are connected to each other.
In this case, since a part of the anisotropic conductive film is overlaid on a part of the overcoat layer beforehand, whereby the anisotropic conductive film can be reliably overlaid on a part of the overcoat layer.
After the anisotropic conductive film is provided so that the overcoat layer is not overlaid with the anisotropic conductive film, the terminal portions and the external circuit connecting portions may be connected to each other in a state in which a part of the overcoat layer is overlaid with a part of the anisotropic conductive film by a flow thereof when the anisotropic conductive film is melted.
In this case, by using a flow of the anisotropic conductive film when it is melted, the anisotropic conductive film can be overlaid on a part of the overcoat layer.
An electronic apparatus of the present invention comprises one of the liquid crystal devices described above.